Change mermaid rendering to witdth 100%

Problem to solve

When we use the mermaid diagrams https://mermaidjs.github.io/#/ in Gitlab to draw the system structure, the rendering can exceed the width of the Markdown pages. Changing the style of the rendering to:

<style>
.mermaid

{ width:100%; }
</style>

makes the system structure to be displayed in a correct way.

Intended users

Further details

Have the chance to visualize the README.md files with diagrams in a correct way

Proposal

Change mermaid style to:

<style>
.mermaid

{ width:100%; }
</style>